Are you supposed to clean a betta tank if they lay eggs?

Cleaning the tank during this point can disrupt the breeding pair and cause them to abandon the eggs, which can result in the eggs not hatching or the fry not surviving. 

If you need to clean the tank because of water quality, perform a small water change and avoid disturbing the breeding pair. However, it's best to avoid cleaning the tank until the eggs have hatched and the fry are free-swimming.